Totally missed this reply @smrutiranjanir - Is this still an issue?
I would go for something like:
pm.test("Date is present in correct format", () => {
jsonData.forEach(obj => {
pm.expect(obj.endDateTime).to.match(/\d{4}-\d{2}-\d{2}\s\d{2}:\d{2}:\d{2}.\d{1}/);
})
});